Cap for a writing instrument



FIG. 1 is a left side perspective view taken from the side and below showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a left side elevational view, the right side elevational view being a mirror image thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a plan view thereof; and,

FIG. 6 is a rear view thereof. 

The ornamental design for a “cap for a writing instrument,” as shown and described. 